Question: Simplify the following expression: $k = \dfrac{20rt}{10t^2} - \dfrac{10rt + 40t^2}{10t^2}$ You can assume $r,s,t \neq 0$.
Explanation: Since the expressions have the same denominator we simply combine the numerators: $k = \dfrac{20rt - (10rt + 40t^2)}{10t^2}$ $k = \dfrac{10rt - 40t^2}{10t^2}$ The numerator and denominator have a common factor of $10t$, so we can simplify $k = \dfrac{r - 4t}{t}$